The Supreme Court of WA heard on Wednesday the pair were engaged in sexual activity in front of the level 13 stairwell door when she started bleeding and became distressed.

She began screaming and Filho, who had a girlfriend at the time, put his hand over her mouth in a bid to silence her.

Mehreen Ahmad, the Pakistani exchange student.

They struggled and she fell headfirst down the stairs trying to get away from him.

The court heard he hit her head against the ground, inflicting traumatic brain injuries and facial fractures, and she fell down a second set of stairs, again trying to escape.

Witnesses who heard thuds coming from the stairwell went to investigate and saw her face down in a pool of blood.

Filho, who claims he then tried to put her in a recovery position, fled the scene and was arrested hours later at his Inglewood home.

Ms Ahmad was placed in an induced coma at Royal Perth Hospital and needed a tracheotomy to breathe.

About three months later, she was treated at one of the world's best rehabilitation centres for brain injuries in the US but still cannot move, communicate or feed herself and is incontinent.

She is not expected to substantially recover and needs constant care.

"She remains unresponsive to this day," her mother said in her victim impact statement, which she read to the court via audio link from Pakistan.

Mehreen Ahmad will never recover from her brain injury.

"As parents, we have to reconcile that we'll never have our daughter back.

"She is now a shell.

"If she had died that day, we would, I think, have come to terms with that loss.

"We are instead trapped in what feels like a never-ending darkness."

She said her daughter was "on top of the world" on the day of the attack, having completed her last exam.

Defence counsel Linda Black read out a letter from her client, who admitted his actions were "despicable", describing them as a "grotesque attempt to quieten her down", but said they were not premeditated.